Method for deciding a bevel curve, method for determining the locus of a bevel, method for processing a lens and apparatus for processing a lens

ABSTRACT

When a forming a bevel on a lens, the value of the bevel curve is calculated based on the value of the curve of the concave face, a reference axis of the bevel curve is determined to be in the same direction as the curvature of the concave face, a reference position on the peripheral edge of the lens in the first portion having the minimum thickness is determined based on the thickness of the first portion, a correction for the initial reference axis of the bevel curve is obtained, an angle of inclination from the direction of the initial reference axis of the bevel curve is obtained based on the correction and the locus of the bevel is determined based on the value of the bevel curve, the reference position and the angle of inclination.

FIELD OF THE INVENTION

The present invention relates to a method for determining a bevel curve,a method for determining a locus of a bevel, a method for processing alens and an apparatus for processing a lens that is used for conductingthese methods.

BACKGROUND OF THE INVENTION

Previously in the art of processing lenses for eyeglass spectacles andthe like, apparatuses for processing a lens have been used to process anuncut lens to fit the shape of a lens frame of a spectacle frame.Various prior art apparatuses for processing a lens are known; althoughcertain lens processing apparatuses having the so-called “function ofautomatic beveled processing” have been provided. When a regular lens isused as the uncut lens and processed using this type of lens processingapparatus with the automatic beveled processing feature, specificadditional information is required to process the lens besides theconventional data required. Specifically, data describing the shape ofthe frame is necessary in addition to the conventional informationrequired for processing the uncut lens. When all of this information isprovided to the apparatus having the automatic beveled processingfeature, the apparatus automatically calculates a locus of a bevel mostsuitable for the lens undergoing processing and the bevel is formedalong this calculated locus.

On the other hand, when the uncut lens is a special lens, such as a highpower minus lens, a high power plus lens, an EX lens or a lenticularlens, the prior art lens processing apparatuses having the automaticbeveled processing feature have certain drawbacks. Specifically, whenprocessing a special lens using a prior art apparatus, the position ofthe apex of the bevel and the bevel curve, or the bevel ratio, must bemanually set by an operator who watches a computerized simulationdisplay. Therefore, adjustment of the position of the apex of the beveland the bevel curve, or the bevel ratio, must be performed intentionallyby the operator.

However, the manual setting of the locus of a bevel depends to a greatdegree on the skill and the experience of the operator. Therefore, it isdifficult that the bevel is formed at a suitable position without askilled operator.

In particular, it is difficult to achieve formation of the most suitablebevel having an excellent balance in these special lenses, such as thehigh power minus lens, the high power plus lens, the EX lens and thelenticular lens. Occasionally, as a result of manually setting the locusof the bevel, when the processing of the special lens is completed andthe special lens is fitted into the intended lens frame, peripheraledges of the processed special lens protrudes unevenly from the rim, andthe appearance of the entire spectacle glass is poor.

In recent years, the number of the skilled operators, who are able toaccurately set the locus of the bevel while processing a special lens,is decreasing. Under these circumstances, there is a need fortechnology, which enables even persons not skilled in the art of lensprocessing to form a suitable bevel in the special lenses.

The present invention has, as an object, enabling persons not skilled inthe art of lens processing to form a suitable bevel in special lensesusing an improved apparatus having an automatic bevel processingfeature.

SUMMARY OF THE INVENTION

According to a first method embodiment, the present invention provides amethod for determining a locus of a bevel in an EX lens comprisingdetermining: the value of the bevel curve based on a value of a curve ofa concave face of the EX lens; determining a first reference position ona peripheral edge in a portion having a minimum thickness at a lowerside in a vertical direction of the EX lens based on a thickness of theportion having a minimum thickness; determining a second referenceposition on a peripheral edge in a portion having a maximum thickness atan upper side in a vertical direction of the EX lens based on a ratio ofa thickness of the portion having a maximum thickness to the thicknessof the portion having a minimum thickness and data of a shape of the EXlens to be obtained by the processing; and, determining a locus of thebevel based on the value of the bevel curve, the first referenceposition and the second reference position.

As the second aspect, the present invention provides a method fordetermining a locus of a bevel in an EX lens comprising: determining thevalue of the bevel curve based on a value of a curve of a concave faceof the EX lens; determining an initial reference axis of the bevel curvein a same direction as a direction of a curvature of the concave face ofthe EX lens; determining a reference position of the bevel on aperipheral edge in a portion having a minimum thickness at a lower sidein a vertical direction of the EX lens based on a thickness of theportion having a minimum thickness; obtaining the value of correctionfor the initial reference axis of the bevel curve based on a ratio of athickness of a portion having a maximum thickness at an upper side in avertical direction of the EX lens to a thickness of the portion having aminimum thickness; obtaining an angle of inclination of a reference axisof the bevel curve from a direction of the initial reference axis of thebevel curve based on the value of correction for the initial referenceaxis of the bevel curve and data of a shape of the EX lens to beobtained by the processing; and, determining the locus of the bevelbased on the value of the bevel curve, the reference position of thebevel and the angle of inclination of the axis.

As the third aspect, the present invention provides a method fordetermining a locus of a bevel in a high power minus lens comprising:determining the value of the bevel curve based on a value of a curve ofa convex face of the high power minus lens; determining a referenceposition on a peripheral edge in a portion having a minimum thickness ofthe high power minus lens at a side of a nose of a person wearing thehigh power minus lens based on a thickness of the portion having aminimum thickness; determining a second reference position on aperipheral edge in a portion having a maximum thickness of the highpower minus lens at a side of an ear of a person wearing the high powerminus lens based on a ratio of a thickness of the portion having amaximum thickness to the thickness of the portion having a minimumthickness and data of a shape of the high power minus lens to beobtained by the processing; and, determining the locus of the bevelbased on the value of the bevel curve, the first reference position andthe second reference position.

As the fourth aspect, the present invention provides a method fordetermining a locus of a bevel in a high power minus lens comprising:determining the value of the bevel curve based on a value of a curve ofa convex face of the high power minus lens; determining an initialreference axis of a bevel curve in a same direction as a direction of acurvature of the convex face of the high power minus lens; determining areference position of the bevel on a peripheral edge in a portion havinga minimum thickness of the high power minus lens at a side of a nose ofa person wearing the high power minus lens based on a thickness of theportion having a minimum thickness; calculating a value of correctionfor the initial reference axis of the bevel curve based on a ratio of athickness of a portion having a maximum thickness of the high powerminus lens at a side of an ear of a person wearing the high power minuslens and a thickness of the portion having a minimum thickness;calculating an angle of inclination of a reference axis of the bevelcurve from a direction of the initial reference axis of the bevel curvebased on the value of correction for the initial reference axis of thebevel curve and data of a shape of the high power minus lens to beobtained by the processing; and, determining the locus of the bevelbased on the value of the bevel curve, the reference position of thebevel and the angle of inclination of the axis.

As the fifth aspect, the present invention provides a method fordetermining a locus of a bevel in a lenticular lens comprising:determining the value of the bevel curve based on a value of a curve ofa concave face of the lenticular lens; determining the referenceposition of the bevel on a peripheral edge in a portion having a minimumthickness at a side of a nose or a ear of a person wearing thelenticular lens based on a thickness of the portion having a minimumthickness; determining a correction for a value of a curve based on aratio of the thickness of the portion having a minimum thickness of thelenticular lens at a side of a nose or an ear to a thickness of aportion having a maximum thickness of the lenticular lens in a verticaldirection; and, determining the locus of the bevel by adding thecorrection for a value of a curve to the value of the bevel curve andpasses through the reference position of the bevel.

As the sixth aspect, the present invention provides a method fordetermining a locus of a bevel in a high power plus lens comprising:determining the value of the bevel curve based on a value of a curve ofa concave face of the high power plus lens; determining the referenceposition of the bevel on a peripheral edge in a portion having a minimumthickness of the high power plus lens based on a thickness of theportion having a minimum thickness; determining a correction for a valueof a curve based on a ratio of the value of a curve of the concave faceto a value of a curve of a convex face of the high power plus lens orbased on the value of a curve of a convex face alone of the high powerplus lens; and, determining the locus of the bevel by adding thecorrection for a value of a curve to the value of the bevel curve andpasses through the reference position of the bevel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically exhibiting the functioningportions of the apparatus for processing a lens in accordance with anapparatus embodiment of the present invention.

FIG. 2 is a perspective diagram schematically exhibiting theconstruction of the interior of the apparatus for processing a lens inaccordance with an apparatus embodiment of the present invention.

FIG. 3 is a diagram exhibiting the construction around thelens-measuring portion of the apparatus for processing a lens inaccordance with an apparatus embodiment of the present invention.

FIG. 4 shows a flow chart describing method steps of the workings of theapparatus for processing a lens as a method embodiment of the presentinvention.

FIG. 5 shows a flow chart describing the method for determining thelocus of the bevel of an EX lens.

FIG. 6 shows a flow chart describing the method for determining thelocus of the bevel of a high power minus lens.

FIG. 7 shows a flow chart describing the method for determining thelocus of the bevel of a lenticular lens.

FIG. 8 shows a flow chart describing the method for determining thelocus of the bevel of a high power plus lens.

FIG. 9 is a diagram exhibiting an example of the display in the displayportion of the apparatus for processing a lens as an apparatusembodiment of the present invention.

FIG. 10 is a diagram describing the method for determining the locus ofthe bevel of an EX lens.

FIG. 11 is a diagram describing the method for determining the locus ofthe bevel of a high power minus lens.

FIG. 12 is a diagram describing the method for determining the locus ofthe bevel of a lenticular lens.

FIG. 13 is a diagram describing the method for determining the locus ofthe bevel of a high power plus lens.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

The present invention includes both apparatus and method embodiments forprocessing a special lens, such as a high power plus lens, a high powerminus lens, a lenticular lens and an EX lens, wherein the apparatus andmethod include an automatic beveled lens processing feature. The variousapparatus and method embodiments are described below in detail withreference to the figures, wherein like character references indicatelike parts or features.

FIG. 1 is a block diagram schematically exhibiting the functionalportions of the apparatus for processing a lens as an apparatusembodiment of the present invention. The apparatus 1 for processing alens comprises a lens-processing portion 2 in which an uncut lens isprocessed so as to provide a processed lens having a shape fitting thelens frame of the spectacle frame (not shown). The apparatus 1 alsoincludes an operation panel 3, a control portion 4 and a memory portion5.

The lens-processing portion 2 comprises a lens-holding unit 21, alens-measuring portion 22, a rough processing portion 23, a beveled andflat grinding portion 24, a polishing portion 25, a grooving portion 26and a chamfering portion 27.

The lens-holding unit 21 comprises, as shown in FIG. 2, a pair oflens-holding shafts 211 and 212 extending in the direction of theoptical axis of an uncut lens L. The uncut lens is held between the twolens-holding shafts 211 and 212 at both faces of the uncut lens L. Theuncut lens L is rotated around the lens center by the lens-holdingshafts so that the position of the processing and the position of themeasurement in the circumferential direction are moved. Due to thisconstruction, procedures progressing from the measurement of the lens tothe processing of the lens can be conducted in a singe chuck operationwithout releasing the chucking after the uncut lens L is held by thelens-holding unit 21.

The lens-measuring portion 22 comprises, as shown in FIG. 3, a pair ofstyluses 221 and 222 which are disposed at opposite sides of the uncutlens L so as to face each other. By bringing the styluses 221 and 222into contact with the concave face and the convex face, respectively, ofthe uncut lens L, the position of the contact (also referred to as “theposition of the face of the lens”) and the thickness of the lens at theposition of the contact are measured. In other words, the lens-measuringportion 22 performs the measurement of the uncut lens L.

The rough processing portion 23 comprises, as shown in FIG. 2, a roughgrinder 231 for a plastic lens and a rough grinder 232 for a glass lens.

The bevel and flat grinding portion 24 comprises a grinder 241 forbeveled processing and flat processing, which comprises a beveledgrinding portion having a groove corresponding to the bevel on thegrinding face and a flat grinding portion having a flat grinding face.Grinder 241 is a finishing grinder.

The polishing portion 25 comprises a polishing grinder 251.

These grinders 231, 232, 241 and 251 are disposed on the same rotatingshaft as shown in FIG. 2. The uncut lens L held by the lens-holding unit21 is pressed against one of these grinders, which are rotated by therotation of the rotating shaft, and the processing is conducted inaccordance with the selected grinder.

The grooving portion 26 comprises a grooving tool having an end mill.The peripheral face of the lens L, after it has been processed to aprescribed peripheral shape, is cut into the prescribed depth by the endmill while the lens L is continuously rotated so that a groove can beformed.

The chamfering portion 27 comprises a chamfering tool having a grindingportion, which has an approximately hemispherical shape. The edge at theboundary between the peripheral face of the lens L and the central ormain face of the lens L, both faces of which have been processed by theflat grinding or the beveled grinding, is ground by the grinding portionhaving the approximately hemispherical shape while the lens L iscontinuously rotated so that the chamfering can be conducted.

The operation panel 3 comprises a display portion 31 and an inputportion 32. The display portion 31 is for displaying an estimated shapeof the lens to be obtained after lens processing as well as the variousinformation values or parameters set for processing. The input portion32 is for inputting information necessary for processing the uncut lensL and for directing a particular desired processing.

The control portion 4 comprises a CPU and other devices, and controlsoperations of the apparatus 1 for processing a lens by executing thecontrol program stored in the memory portion 5.

The memory portion 4 comprises ROM, RAM and other devices, and memorizesthe control program of the apparatus 1 for processing a lens, datacorresponding to the image of the lens, and other information.

In FIG. 1, a frame tracer is shown that is attached at the outside ofthe apparatus 1 for processing a lens, and which can communicate withthe apparatus 1. The frame tracer F is used to measure the desiredspectacle frame set and transfers data corresponding to thethree-dimensional shape of the lens frame to the apparatus 1 forprocessing a lens. Therefore, the apparatus 1 for processing a lens isequipped with an interface for communicating with the frame tracer F.Although frame tracer F is generally not a component constituting aportion of the apparatus 1 for processing a lens, the apparatus 1 forprocessing a lens may be constructed so that the frame tracer F doesconstitute and integral component of the apparatus 1.

The workings of the apparatus 1 for processing a lens will be describedas follows with reference to FIG. 4. According to the method shown inFIG. 4, the first step S1 includes obtaining data corresponding to theshape of the lens frame of the spectacle frame by measuring the shape ofthe lens frame using the frame tracer F.

In the second step S2 of the method, the operator sets the uncut lens Lin the lens-holding unit 21, and directs the holding of the lens usingthe input portion 32. By this lens holding operation, the uncut lens Lis held by the lens-holding unit 21 in a chucked condition. While theuncut lens L is held, the optical center of the uncut lens L is placedin the axial direction of the lens-holding shafts 221 and 222 of thelens-holding unit 21.

In the third step S3 according to the method, a layout display 91, suchas that shown in FIG. 9, is displayed in the display portion 31 whilethe lens-holding unit 21 is holding the uncut lens L. Using the inputportion 32 to manipulate the layout display 91, the operator indicateswhether the lens to be processed is a lens for the right eye, or for theleft eye, and also indicates in a column 911 that the type of theprocessing selected is bevel processing. The operator inputs the datacorresponding to the prescription for the person who will be wearing thespectacle glasses, and other information required by the layout toinclude data corresponding to the distance between geometrical centersof the right and left spectacle lenses into a column 912, by using theinput portion 32. When these operations that input data for the displayhave been conducted, the control portion 3 obtains, by a calculationbased on the input data, the “data of the shape of processing,” which isthat data expressing, describing, or corresponding to, the shape of thelens formed after the rough grinding of the uncut lens L. The “data ofthe shape of processing” can also be referred to as the “shapeprocessing data.”

At this time, the operator may select, using the input portion 32,chamfering and/or grooving as an option for finishing the uncut lens.

Examples of other data corresponding to the prescription of an eyeglassspectacle include the “pupillary distance” (PD), information on the eyepoint including the height of the eye point relative to the geometricalcenter of the frame and data expressing the cylinder axis (AX). Examplesof data corresponding to the distance between geometrical centersinclude: (a) the “frame pupillary distance” (FPD) expressing thedistance between the geometrical centers of the lens frames, and (b) the“distance between lenses” (DBL) expressing the distance between theperipheries of the right and left lenses (the so called “nose width”).

In the fourth step S4, the operator then inputs the lens datacorresponding to the uncut lens L by using the input portion 32.

Examples of the lens data include: (a) the value of a curve, or thevalue of a curve for every axial direction of the convex face, of theuncut lens, (b) the value of a curve, or the value of a curve for everyaxial direction of the concave face, of the uncut lens, (c) thethickness of the center (i.e., the optical center or the geometricalcenter) of the uncut lens, (d) the diameter of the lens (including Asize and B size), (e) the shape of the lens (the shape of the nearoptical center), and (f) the distance between the optical center and thegeometrical center.

The above values of a curve may be approximate values. In addition, whenprocessing an uncut lens, all these lens data inputs are not alwaysnecessary. The necessary data may be selected and included dependingupon choices made by the operator. Furthermore, the lens data may beprovided directly to the apparatus 1 for processing a lens through adata communication link with another apparatus, or by the manual inputprovided by the operator.

In the fifth step S5, the operator then indicates, in column 913 of theinput display 91, the type of uncut lens L to be processed by using theinput portion 32. More specifically, the input portion 32 has a buttonfor selecting the type of lens to be processed. By pushing the lens typeselection button, any one of either special lenses (i.e., EX,minus-power, lenticular, plus-power) and regular lenses can be selectedas the type of lens to be processed. For example, in FIG. 5, the EX lenshas been selected for processing.

When the operator indicates the lens type of the uncut lens to beprocessed, by using the input portion 32 as described above, the controlportion 4 then obtains this lens type information (also referred to as“the step of obtaining the information of the lens type”). Lens typeinformation may be provided directly to the apparatus 1 for processing alens 1 from an external source by means of some form of electroniccommunication, or the lens type information may be manually inputted bythe operator.

For the purposes of this disclosure, the following are defined. The highpower minus lens and the high power plus lens are meant to includelenses having a maximum thickness of the peripheral lens edge of about 5mm or greater after the lens is processed. Since the size of theprotruding portion of these lenses is great when fitted into frames, itis desirable that the bevel be accurately formed at a suitable position.

In the sixth step S6, the operator then pushes the starting switch ofthe input portion 32, which activates the control portion 3 to directthe measuring of the shape of the uncut lens L using lens-measuring unit22 based on the processing shape data obtained in step S3. The styluses221 and 222 are moved relative to the uncut lens L, which is held by theholding shafts 211 and 212, in a manner such that the positions ofcontact of the styluses 221 and 222 on the faces of the uncut lens formparticular loci. These loci are about the same as that of the positionof the peripheral edge of the lens after processing. While the styluses221 and 222 are in the positions of contact, both the positions ofcontact (i.e., the positions on the faces of the lens in contact withthe styluses) and the thickness of the lens at the positions of thecontact are measured by the lens-measuring unit 22.

In the seventh step S7 (also referred to as “the step of calculating thelocus of a bevel”), the control portion 4 calculates the locus of thebevel in accordance with the selected lens type based on the informationcorresponding to the selected lens type obtained in step S5 (the step ofobtaining the information of the lens type) and calculates the datacorresponding to the locus of the bevel, which is also referred to asthe “data of the automatically set bevel curve” or as the “automaticallyset bevel curve data.”

Step S7 includes five different pathways depending upon what type oflens is being processed. In other words, step S7 is conductedspecifically for each lens type selected from the group consisting of“EX” (step S71), “high power minus” (step S72), “lenticular” (step S73),“high power plus” (step S74) and “regular” (step S75) lenses. The stepspecific for each lens type will be described later in detail; however,the general idea of step S7 is to provide a method for determining thelocus of a bevel in the lens to be processed. Because there are multipledifferent lens types, step S7 includes the five different pathways,wherein each pathway provides the sub-steps for the method fordetermining the locus of a bevel in a particular one of the five lenstypes to be processed. When a “regular” lens is selected (step S75),more specific description of the step S75 will be omitted since theprocedures are well known.

In the eighth step S8, the control portion 4 directs the display portion31 to display a “sample” of the condition set for the bevel based on thedata of the locus of the bevel calculated in step S7. Then, the operatorcan modify or adjust the condition of the automatically set bevel(including the position and the angle of the bevel) using the inputportion 32. When such a modification is made, the data of the locus ofthe bevel is modified from the sample conditions previously calculatedin step S7.

In the ninth step S9, the operator initiates processing using the inputportion 32. When the control portion 4 detects the operator's directionto start processing the lens L, the control portion 4 computes datacorresponding to rough processing based on the data of the shape ofprocessing obtained in S3. The “data of the rough processing,” which isthe rough processing data, includes data showing the rough processinggrinding margins. The control portion 4 then controls thelens-processing portion 2 so that the rough processing of the uncut lensis conducted in accordance with the computed rough processing data.Subsequently, the peripheral portion of the uncut lens L is ground bythe rough grinder 231 for a plastic lens or the rough grinder 232 for aglass lens, depending upon whether lens L is plastic or glass. Thenature of the material of lens L is data that would be inputted intoapparatus 1 during step S4 using input portion 32.

In the tenth step S10, the control portion 4 then computes “data of thebevel processing,” also referred to as “bevel processing data,” based onthe data of the locus of the bevel (also referred to as the “bevel locusdata”) computed in step S7 (so, the “modified bevel locus data”corresponds to the data that has been modified in step S8) and the shapeprocessing data obtained in step S3. The control portion 4 forms thebevel based on the bevel processing data thus computed. In this manner,the peripheral edge of the roughly processed lens is processed, and thedesired bevel is formed by the finishing grinder provided by the grinder241 for beveled processing and flat processing. The bevel groove isformed by the grooving portion 26 of the finishing grinder.

When the lens for the right eye has been fully processed in accordancewith the above steps S1 through S10, the operation returns to step S2.The uncut lens for the lens for the left eye is held by chucking, andthe lens for the left eye is fully processed in accordance with the sameprocedures S2 through S10.

As mentioned above, step S7 is described more fully as follows.

Special lens processing when the lens is an EX lens

In the case where an EX lens is indicated, step S7 performs step S71.Step S71 will be described in accordance with the flow chart shown inFIG. 5 with reference to the diagram shown in FIG. 10. Step S71 includessub-steps S711 through S716.

In step S711, the value of the bevel curve K1 is computationallydetermined based on the value of the curve of the concave face of the EXlens contained in the lens data inputted in step S4 described above.Step S711 is referred to as “the step of determining the value of thebevel curve, and this step is a computational step that determines, bycalculation, the “value of the bevel curve” (also referred to as the“bevel curve value”) for the EX lens. Specifically, this calculationdiffers depending on whether the EX lens is a minus-power lens or aplus-power lens. The value of the bevel curve K1 is calculated inaccordance with one of the following equations:

In the case of a plus-power lens:K 1=(average value of the curve at the concave side)×(adjustingcoefficient e ₊)

In the case of a minus-power lens:K 1=(average value of the curve at the concave side)×(adjustingcoefficient e ⁻)In the above equations, e₊ represents a number of 1 or greater and e⁻represents a number of 1 or smaller. In other words, e₊≧1 and e⁻≦1.

When the refractive index of the lens material is 1.523, the computedvalue of the bevel curve K1 and the radius of curvature r1 of the bevelcurve r1 satisfy the following equation:K 1≈523/r 1wherein the refractive index of the air is set at 1.0.

In step S712, which follows the calculation step S711, the referenceaxis of the bevel curve (hereinafter, referred to as the “initialreference axis of the bevel curve”) is determined to be in the samedirection as the direction of the curvature of the concave face of theEX lens. Thus, step S712 is referred to as “the step of determining theinitial reference axis of the bevel curve.”

Step S713 follows step S712. In step S713, the first reference positionm, which is on the peripheral edge of the lens in the portion having theminimum thickness at the lower side in the vertical direction of the EXlens (see FIG. 10), is decided. Position m is referred to as “thereference position of the bevel” of the lens and is based on thethickness t1 of the portion having the minimum thickness. Step S713 isreferred to as the “step of determining the first reference position.”In this step, the first reference position m is expressed by thedistance P1 from the end of the peripheral edge at the side of theconvex face in the portion having the minimum thickness to the firstreference position m. Specifically, P1 differs depending on thethickness t1 of the portion having the minimum thickness and is decidedin the following manner:

-   -   When t1=2.4 mm or smaller, P1=t1/2    -   When t1=2.4˜4.0 mm, P1=1.2    -   When t1=4.0 mm or greater, P1=3×t1/10

Step S714 follows step S713. In step S714, the second reference positionn, which is on the peripheral edge in the portion having the maximumthickness at the upper side in the vertical direction of the EX lens(see FIG. 10), is decided based on the ratio (t2/t1) of the thickness t2of the portion having the maximum thickness to the thickness t1 of theportion having the minimum thickness. Step S714 is referred to as the“step of determining the second reference position.” The secondreference position n is expressed by the distance H from the positionm′, corresponding to the first reference position on the peripheral edgein the portion having the maximum thickness, to the second referenceposition n. Hereinafter, the distance H is referred to as “the value ofcorrection for the reference axis of a curve”. Specifically, the valueof correction for the reference axis of a curve H is calculated inaccordance with the following equation:H=a×(t 2/t 1)×(t 1−P 1)−(t 1−P 1)wherein a represents an adjusting coefficient. The term (t2/t1) is 1 orgreater. When a×(t2/t1) would be 1 or smaller, a×(t2/t1) is always setto equal 1 (i.e., a×(t2/t1)=1). In other words, the value for a×(t2/t1)is not allowed to be less than 1.

Step S715 follows step S714. In step S715, the angle of inclination θ ofthe axis from the direction of the initial reference axis of the bevelcurve is calculated based on the value of correction for the referenceaxis of a curve H and the B size, which is the value of the verticalaxis of the lens shape shown in FIG. 10. The B size is contained in thelens data inputted in step S4. Step S715 is referred to as “the step ofcalculating the angle of inclination of the axis.” Specifically, theangle of inclination θ of the axis is calculated in accordance with thefollowing equation:θ=arctan(H/B)

Step S716 follows step S715 and is referred to as “the step ofdetermining the locus of the bevel.” In step S716, the locus of thebevel is determined based on the value of the bevel curve K1, the firstreference position m, and the angle of inclination θ of the axis.Specifically, the locus of the bevel has the value of the bevel curve K1and an axis determined by inclination of the initial reference axis ofthe bevel curve by the angle θ in the anti-clockwise direction as shownin FIG. 10. Thus, step S716 determines that the locus of the bevel isthe reference axis of the curve. The determined locus of the bevel,computed in accordance with the procedure discussed above, has the valueof the bevel curve K1 and passes through the first reference position mand the second reference position n.

In accordance with the above procedures, a suitable locus of the bevelhaving an excellent balance can be calculated that avoids markedprotrusion of the front face of the EX lens beyond the rim of the framewhen the EX lens is fitted into the frame.

Special lens processing when the lens is a high power minus lens

In the case where a high power minus lens is indicated, step S7 performsstep S72. Step S72 will be described in accordance with the flow chartshown in FIG. 6 with reference to the diagram shown in FIG. 11. Step S72includes sub-steps S721 through S726.

In step S721, the value of the bevel curve K1 is computationally decidedbased on the value of the curve of the convex face of the high powerminus lens contained in the lens data inputted in step S4 describedabove. Step S721 is referred to as “the step of determining the value ofthe bevel curve, and is a computational step that determines, bycalculation, the value of the bevel curve (“bevel curve value”) for thehigh power minus lens. Specifically, the calculation differs dependingon the value of the curve C of the convex face of the high power minuslens. The value of the bevel curve K1 is calculated in accordance withone of the following equations:

-   -   When the value of the curve C of the convex face is 2.0 or        smaller,        K1=3.0    -   When the value of the curve C of the convex face is 2.0˜4.0,        K 1=(C−2.0)/2+3.0    -   When the value of the curve C of the convex face is 4.0˜7.0,        K1=C    -   When the value of the curve C of the convex face is 7.0 or        greater,        K1=7.0

When the refractive index of the lens material is 1.523, the computedvalue of a bevel curve K1 and the radius of curvature of the curve r1satisfy the following equation:K 1≈523/r 1wherein the refractive index of the air is set at 1.0.

In step S722, which follows the calculation step S721, the referenceaxis of the bevel curve (hereinafter, referred to as the “initialreference axis of the bevel curve”) is decided to be in the samedirection as the direction of the curvature of the convex face of thehigh power minus lens. Thus, step S722 is referred to as “the step ofdetermining the initial reference axis of the bevel curve.”

Step S723 follows step S722. In step S723, the first reference positionm, which is on the peripheral edge of the lens in the portion having theminimum thickness at the side of the nose of the person wearing the highpower minus lens (see FIG. 11), is decided. Position m is referred to asthe “reference position of the bevel” of the lens and is based on thethickness t1 of the portion having the minimum thickness. Step S723 isreferred to as “the step of determining the first reference position.”In this step, the first reference position m is expressed by thedistance P1 from the end of the peripheral edge at the side of theconvex face in the portion having the minimum thickness to the firstreference position m. Specifically, P1 differs depending on thethickness t1 of the portion having the minimum thickness and is decidedin the following manner:

-   -   When t1=2.4 mm or smaller, P1=t1/2    -   When t1=2.4˜4.0 mm, P1=1.2    -   When t1=4.0 mm or greater, P1=3×t1/10

Step S724 follows step S723. In step S724, the second reference positionn, which is on the peripheral edge in the portion having the maximumthickness (see FIG. 11), is decided based on the ratio (t2/t1) of thethickness t2 of the portion of the high power minus lens having themaximum thickness of the high power minus lens at the side of the ear ofthe person wearing the high power minus lens to the thickness t1 of theportion having the minimum thickness. Step S724 is referred to as “thestep of determining the second reference position.” The second referenceposition n is expressed by the distance H from the position m′,corresponding to the first reference position on the peripheral edge inthe portion having the maximum thickness, to the second referenceposition n. Hereinafter, the distance H is referred to as the “value ofcorrection for the reference axis of a curve.” Specifically, the valueof correction for the reference axis of a curve H is calculated inaccordance with the following equation:H=P 1×a×(t 2/t 1)−P 1wherein a represents an adjusting coefficient. (t2/t1) is 1 or greater.When a×(t2/t1) would be 1 or smaller, a×(t2/t1) is always set to equal 1(i.e., a×(t2/t1)=1). In other words, the value for a×(t2/t1) is notallowed to be less than 1.

Step S725 follows step S724. In step S725, the angle of inclination 0 ofthe axis from the direction of the initial reference axis of the bevelcurve is calculated based on the value of correction for the referenceaxis of a curve H and the A size, which is the value of the horizontalaxis of the lens shape shown in FIG. 11. The A size is contained in thelens data inputted in step S4. Step S725 is referred to as “the step ofcalculating the angle of inclination of the axis.” Specifically, theangle of inclination 0 of the axis is calculated in accordance with thefollowing equation:θ=arctan(H/A)

Step S726 follows step S725 and is referred to as “the step ofdetermining the locus of the bevel.” In step S726, the locus of thebevel is determined based on the value of the bevel curve K1, the firstreference position m and the angle of inclination θ of the axis.Specifically, the locus of the bevel has the value of the bevel curve K1and an axis determined by inclination of the initial reference axis ofthe bevel curve by an angle θ in the clockwise direction as shown inFIG. 11. Thus, step S726 decides that the locus of the bevel is thereference axis of the curve. The decided locus of the bevel, computed inaccordance with the procedure discussed above, has the value of thebevel curve K1 and passes through the first reference position m and thesecond reference position n.

In accordance with the above procedures, a suitable locus of the bevelhaving an excellent balance can be calculated that avoids markedprotrusion of the back face of the high power minus lens beyond the rimof the frame when the high power minus lens is fitted into the frame.

Special lens processing when the lens is a lenticular lens

In the case where a lenticular lens is indicated, step S7 performs stepS73. Step S73 will be described in accordance with the flow chart shownin FIG. 7 with reference to the diagram shown in FIG. 12. Step S73includes sub-steps S731 through S734.

In step S731, the value of the bevel curve K1 is computationallydetermined based on the value of the curve of the concave face of thelenticular lens contained in the lens data inputted in step S4 describedabove. Step S731 is referred to as “the step of determining the value ofthe bevel curve,” and this step is a computational step that determines,by calculation, the “value of the bevel curve” (also referred to as the“bevel curve value”). Specifically, the value of the bevel curve K1 iscalculated in accordance with the following equation:K 1=(average value of the curve at the concave side)×(adjustingcoefficient e)In the above equations, e represents a number of 1 or greater (i.e., e≧1).

When the refractive index of the lens material is 1.523, the computedvalue of the bevel curve K1 and the radius of curvature of the curve r1satisfy the following equation:K 1≈523/r 1wherein the refractive index of the air is set at 1.0.

In step S732, which follows the calculation step S731, the referenceposition of the bevel m, which is on the peripheral edge of the lens inthe portion having the minimum thickness at the side of the nose or theear of the person wearing the lenticular lens (see FIG. 12), isdetermined based on the thickness t1 of the portion having the minimumthickness. Step S732 is referred to as “the step of determining thefirst reference position.” In this step, the reference position of thebevel m is expressed by the distance P1 from the end of the peripheraledge at the side of the convex face in the portion having the minimumthickness to the first reference position m. Specifically, P1 differsdepending on the thickness t1 of the portion having the minimumthickness and is determined in the following manner:

-   -   When t1=2.4 mm or smaller, P1=t1/2    -   When t1=2.4˜4.0 mm, P1=1.2    -   When t1=4.0 mm or greater, P1=3×t1/10

Step S733 follows step S732 and is referred to as “the step ofdetermining the correction for the value of the curve.” In step S722,the correction for the value of the curve S is determined based on theratio (t2/t1) between the thickness t1 of the portion of the lenticularlens having the minimum thickness at the side of the nose or the ear ofthe person wearing the lenticular lens and the thickness t2 of theportion having the maximum thickness in the vertical direction of thelenticular lens. Specifically, the correction for the value of the curveS is calculated in accordance with the following equation:S=a×(t 2/t 1)−1wherein a represents an adjusting coefficient. (t2/t1) is 1 or greater.When a×(t2/t1) would be 1 or smaller, a×(t2/t1) is always set to equal 1(i.e., a×(t2/t1)=1). In other words, the value for a×(t2/t1) is notallowed to be less than 1.

Step S734 follows step S733 and is referred to as “the step ofdetermining the locus of the bevel.” In step S734, the locus of thebevel, which has the value of the curve K2 (=S+K1), is determined byadding the correction for the value of the curve S to the value of thebevel curve K1 that passes through the reference position of the bevelm.

In accordance with the above procedures, a suitable locus of the bevelhaving an excellent balance can be calculated that avoids markedprotrusion of the segment in front of the lens when the lenticular lensis fitted into the frame.

Special lens processing when the lens is a high power plus lens

In the case where a high power plus lens is indicated, step S7 performsstep S74. Step S74 will be described in accordance with the flow chartshown in FIG. 8 with reference to the diagram shown in FIG. 13. Step S74includes sub-steps S741 through S744.

In step S741, the value of the bevel curve K1 is computationallydetermined based on the value of the curve of the concave face of thehigh power plus lens contained in the lens data inputted in step S4described above. Step S741 is referred to as “the step of determiningthe value of the bevel curve,” and this step is a computational stepthat determines, by calculation, the “value of the bevel curve” (alsoreferred to as the “bevel curve value”). Specifically, the value of thebevel curve K1 is calculated in accordance with the following equation:K 1=(average value of the curve at the concave side)×(adjustingcoefficient e)In the above equation, e represents a number of 1 or greater.

When the refractive index of the lens material is 1.523, the computedvalue of the bevel curve K1 and the radius of curvature of the curve r1satisfy the following equation:K 1≈523/r 1wherein the refractive index of the air is set at 1.0.

In step S742, which follows calculation step S741, the referenceposition of the bevel m, which is on the peripheral edge of the lens inthe portion having the minimum thickness of the high power plus lens(see FIG. 13), is determined based on the thickness t1 of the portionhaving the minimum thickness. Step S742 is referred to as “the step ofdetermining the first reference position.” In this step, the referenceposition of the bevel m is expressed by the distance P1 from the end ofthe peripheral edge at the side of the convex face in the portion havingthe minimum thickness to the first reference position m. Specifically,P1 differs depending on the thickness t1 of the portion having theminimum thickness and is determined in the following manner:

-   -   When t1=2.4 mm or smaller, P1=t1/2    -   When t1=2.4˜4.0 mm, P1=1.2    -   When t1=4.0 mm or greater, P1=3×t1/10

Step S743 follows step S742 and is referred to as “the step ofdetermining the correction for the value of the curve.” In step S743,the correction for the value of the curve S is determined based on theratio (C2/C1) of the value of the curve C1 of the concave face to thevalue of the curve C2 of the convex face of the high power plus lens, orbased on the value of the curve C2 of the convex face alone.Specifically, the correction for the value of the curve S is calculatedin accordance with the following equation:S=a×(C 2/C 1)−1wherein a represents an adjusting coefficient. (C2/C1) is 1 or greater.When a×(C2/C1) would be 1 or smaller, a×(C2/C1) is always set to equal 1(i.e., a×(C2/C1)=1). In other words, the value for a×(C2/C1) is notallowed to be less than 1

Step S744 follows step S743 and is referred to as “the step ofdetermining the locus of the bevel.” In step S743, the locus of thebevel, which has the value of the curve K2 (=S+K1), is determined byadding the correction for the value of the curve S to the value of thebevel curve K1 that passes through the reference position of the bevelm.

In accordance with the above procedures, a suitable locus of the bevelhaving an excellent balance can be calculated that avoids markedprotrusion of the convex face of the high power plus lens in front ofthe lens when the high power plus lens is fitted into the frame.

Incidentally, “an EX lens” is well known to a person skilled in the artsand is sometimes called “an E line multifocal lens”

In accordance with the present invention, the locus of the bevel, whichhas heretofore been determined by the skill and the experience of askilled operator, can be obtained in accordance with the prescribedprocedures. Therefore, the suitable bevel can be formed even by a personnot skilled in the art.

1-6. (canceled)
 7. A method for determining a bevel curve in alenticular lens, comprising the steps of: inputting a value of a curveof a concave face of the lenticular lens; and calculating a value of thebevel curve based on the inputted value of the curve of the concave faceof the lenticular lens.
 8. A method for determining a bevel curve in alenticular lens as recited in claim 7, wherein the value of the bevelcurve is calculated as follows:K 1=(average value of the curve at the concave face)×(adjustingcoefficient e), wherein K1 represents the value of the bevel curve, ande represents a number of 1 or greater. 9-20. (canceled)
 21. A method fordetermining a locus of a bevel in a lenticular lens comprising the stepsof: calculating a value of a bevel curve based on a value of the curveof a concave face of the lenticular lens; determining a location of areference position of the bevel on a peripheral edge of the lenticularlens in a first portion having a minimum thickness, wherein this firstportion having the minimum thickness is on a side of the lens that isclosest to a wearer's nose, wherein the location of the referenceposition is based on a thickness of the first portion having the minimumthickness; calculating a correction value of a curve based on a ratio ofthe thickness of the first portion having the minimum thickness to thethickness of a second portion having a maximum thickness of thelenticular lens in a vertical direction; and, determining the locus ofthe bevel, having a value of a corrected curve, by adding the correctionvalue of a curve to the value of the bevel curve that passes through thereference position of the bevel.
 22. A method for determining a locus ofa bevel in a lenticular lens as recited in claim 21, wherein thelocation of the reference position is determined based upon thefollowing relationships, wherein when t1=2.4 mm or smaller, thenP1=t1/2; when t1=2.4˜4.0 mm, then P1=1.2; when t1=4.0 mm or greater,then P1=3×t1/10, wherein t1 represents the thickness of the portion ofthe lenticular lens having the minimum thickness at the nose side or theear side of the lens, and P1 represents the distance from the referenceposition to the end of the peripheral edge at the side of the convexface of the lens in the portion having the minimum thickness.
 23. Amethod for determining a locus of a bevel in a lenticular lens asrecited in claim 22, wherein the correction value of the curve iscalculated in accordance with the following equation,S=a×(t 2/t 1)−1, wherein S represents the correction value of the curve,a represents an adjusting coefficient, and t2 represents the thicknessof the portion of the lens that has the maximum thickness in thevertical direction of the lenticular lens. 24-30. (canceled)
 31. Amethod for processing a lenticular lens comprising the step of forming abevel along a locus of a bevel, wherein the locus of the bevel isdetermined in accordance with the method for determining a locus of abevel according to claim
 21. 32-40. (canceled)